In recent years minimally-invasive apparatus and methods for treating narrowing of body vessels, especially the coronary arteries, have been developed as a substitute for invasive surgical procedures, such as bypass grafting. For example, percutaneous transluminal coronary angioplasty ("PTCA") is commonly performed on patients to restore patency to coronary arteries that have become narrowed due to vascular disease and plaque buildup.
Typically, PTCA procedures involve the insertion of a mechanical dilatation device--usually a balloon catheter--transluminally to a constricted location of a coronary artery. The device is then dilated to a selected diameter, and the pressure maintained approximately constant to compress plaque lining the artery, thereby increasing the diameter of the artery and restoring flow therethrough.
A drawback common to PTCA, and dilatation procedures that are performed in other body lumens, is the inability to gauge the diameter of the body lumen. Such information is important for assessing the potential efficacy of a proposed course of therapy, for example, PTCA, PTCA followed by the implantation of a vascular prosthesis, or coronary artery bypass grafting ("CABG"). Often, due to the tortuosity of a vessel, it is difficult to assess the degree of narrowing of the vessel using conventional fluoroscopic and angiographic techniques. In particular, fluoroscopy provides only a two-dimensional view of the vessel, and may not adequately represent the degree of constriction occurring in three dimensions.
One promising method that has been developed to assess the topology of diseased vessels is intraluminal ultrasound technology. Typically, a catheter carrying an ultrasound element is disposed within a diseased vessel to provide a cross-sectional view of the vessel wall (and stenosis) at a given longitudinal location within the vessel. Drawbacks of intraluminal ultrasound systems, however, are that the images are typically fairly noisy, and of such high contrast that they have limited utility. Moreover, because the ultrasound image is in a plane transverse to the vessel axis, it is difficult to obtain an accurate mapping of the vessel along the entire section of the stenotic region. While attempts to construct three-dimensional views of the vessel and stenotic region using offline postprocessing have been made, such systems are expensive, require specialized hardware, and are time consuming, leading to limited acceptance in the medical community.
In view of the foregoing, it would be desirable to provide apparatus and methods for providing, in real-time, a detailed map of the interior surface topology of a vessel, including a stenotic region.
It also would be desirable to provide apparatus and methods for mapping the interior surface topology of a body lumen that employs relatively simple electrical and mechanical components, thereby providing a system that costs less than previously known ultrasound technology, but which provides significantly better performance.
It further would be desirable to provide apparatus and methods for providing, in near real-time, a three-dimensional view of the interior surface of a vessel, using low cost, readily available components.